How to chance radii of many cylinders at the same time?
If they are equal, you can select all of them, Ctrl L Link object data, then if you modify one, every other will be modified as well. Press U to turn back to single user.

To vary the radius of the cylinders without affecting loc and rot, choose the "normal" transform orientation, select the top of one cylinder and click this plus button to create a new custom transform orientation, call it "face normal".



Then choose face normal as active transform orientation, select all vertices of one cylinder and press  S Shift Z Z.